Rod Reducer Assembly

ABSTRACT

A rod reducer assembly is provided and is selectively mountable to a pedicle screw assembly. The pedicle screw assembly includes a pedicle screw housing that defines a rod-receiving recess. The pedicle screw assembly includes an extension assembly that is coupled to the pedicle screw housing by a frangible member. The rod reducer is configured to reduce a spinal rod into the rod-receiving recess of the pedicle screw assembly. The rod reducer assembly may include a derotation sleeve configured to inhibit the frangible member from breaking while manipulating a spinal bone.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.15/850,169, filed on Dec. 21, 2017, which claims the benefit of U.S.Provisional Application Ser. No. 62/440,143, which was filed on Dec. 29,2016, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to spinal surgery and, more particularly,to systems, devices, and methods for reducing spinal rods into pediclescrew housings and/or for manipulation of a spinal column.

BACKGROUND

The human spinal column or spine is a highly complex structure includingtwenty-four discrete bones, known as vertebrae, coupled sequentially toone another to house and protect critical elements of the body's nervoussystem. In between adjacent vertebrae of the spine are discs thatfunction as vertebral shock absorbers for distributing pressureresulting from the impact of the body's activities.

Various disorders, diseases, and injuries can restrict the range ofmotion of the spine and/or interfere with important elements of thenervous system. Spinal fixation apparatus are widely employed insurgical procedures for correcting such spinal conditions. For example,spinal rods can be secured to the spine by spinal fixation fasteners,such as pedicle screws, to straighten abnormal curvature of the spine orto provide spinal stability.

It is desired to perform these procedures efficiently and in a minimallyinvasive manner.

SUMMARY

Accordingly, one aspect of the present disclosure is directed to a rodreducer assembly. The rod reducer assembly includes a pedicle screwhousing that defines a rod-receiving recess and an extension assemblythat extends from the pedicle screw housing. The extension assembly iscoupled to the pedicle screw housing by a frangible member. The rodreducer assembly further includes a rod reducer. The rod reducerincludes a knob and a sleeve assembly. The sleeve assembly includes anouter sleeve and an inner sleeve. The inner sleeve includes a fingerthat is selectively attachable to the extension assembly to secure therod reducer to the extension assembly. The outer sleeve is axiallymovable relative to the inner sleeve to reduce a spinal rod into therod-receiving recess of the pedicle screw housing in response torotation of the knob relative to the sleeve assembly.

In some embodiments, the extension assembly may include a proximalportion defining a groove configured to receive the finger of the rodreducer to selectively attach the rod reducer to the extension assembly.

In certain embodiments, the knob may be coupled to the sleeve assemblyby a retaining ring to enable the knob to rotate relative to the sleeveassembly.

In embodiments, the knob may be threadably coupled to the inner sleeve.

In some embodiments, the knob may be rotatable about the inner sleeve,which, in turn, causes axial translation of the knob and the outersleeve relative to the inner sleeve.

In certain embodiments, the outer sleeve may be transitionable betweenan unreduced position and a reduced position. The rod reducer may befixed to the extension assembly while the outer sleeve is disposed inthe unreduced position. The rod reducer may be removable from theextension assembly while the outer sleeve is disposed in the reducedposition.

According to another aspect, the present disclosure is directed to anassembly including a pedicle screw assembly, a derotation sleevemountable to the pedicle screw assembly, and a rod reducer mountable tothe derotation sleeve.

The pedicle screw assembly includes a screw securable to a spinal boneand a pedicle screw housing mounted to the screw. The pedicle screwhousing defines a rod-receiving recess and includes an extensionassembly coupled to the pedicle screw housing by a frangible member. Thederotation sleeve is movable with the pedicle screw assembly tomanipulate the spinal bone and is configured to inhibit the frangiblemember from breaking while manipulating the spinal bone. The rod reduceris mountable to the derotation sleeve and is configured to reduce aspinal rod into the rod-receiving recess of the pedicle screw.

In some embodiments, the derotation sleeve includes a locking mechanismpositionable between a locked position and an unlocked position. Thederotation sleeve may be movable with the pedicle screw assembly whilein the locked position and may be separable from the pedicle screwassembly while in the unlocked position.

In certain embodiments, the derotation sleeve may include a knob, anupper shaft portion extending from the knob, and a lower shaft portioncoupled to the upper shaft portion.

In embodiments, the upper shaft portion of the derotation sleeve mayinclude a sleeve assembly including an inner sleeve and an outer sleeve.The inner sleeve may be selectively attachable to the extension assemblyof the pedicle screw assembly to secure the derotation sleeve to thepedicle screw assembly.

In embodiments, the inner sleeve may include a finger and the extensionassembly may define a groove configured to selectively receive thefinger.

In certain embodiments, the knob may be rotatable relative to the innersleeve to move the outer sleeve axially relative to the inner sleeve.

In some embodiments, the rod reducer may include a cap that isthreadably engageable with the knob of the derotation sleeve to couplethe rod reducer to the derotation sleeve.

In embodiments, the cap of the rod reducer may be coupled to a sleeveassembly of the rod reducer. The sleeve assembly of the rod reducer mayinclude an outer sleeve and an inner sleeve. The outer sleeve of the rodreducer may be rotatable relative to the cap and the inner sleeve of therod reducer to axially advance the inner sleeve of the rod reducer alongthe pedicle screw assembly and reduce the spinal rod into therod-receiving recess of the pedicle screw housing of the pedicle screwassembly.

According to another aspect, the present disclosure is directed to a rodreducer assembly including a pedicle screw assembly and a rod reducerselectively mountable to the pedicle screw assembly.

The pedicle screw assembly includes a screw securable to a spinal bone,a pedicle screw housing mounted to the screw, and an extension assemblycoupled to the pedicle screw housing by a frangible member. The pediclescrew housing defines a rod-receiving recess.

The rod reducer is selectively mountable to the pedicle screw assemblyand includes a knob assembly and a reduction sleeve coupled to the knobassembly. The knob assembly includes an outer sleeve and an innersleeve. The inner sleeve of the knob assembly is configured toselectively attach to the extension assembly. The reduction sleeveassembly includes a first inner sleeve and a second inner sleeve. Thefirst inner sleeve is axially movable relative to the outer sleeve.

In embodiments, the second inner sleeve of the reduction sleeve may becoupled to the pedicle screw housing.

In some embodiments, the first inner sleeve may move axially relative tothe second inner sleeve in response to rotation of the outer sleeve ofthe knob assembly relative to the first and second inner sleeves.

In certain embodiments, the inner sleeve of the knob assembly mayinclude a finger that selectively couples to the extension assembly.

In embodiments, the outer sleeve of the knob assembly may be configuredto compress the finger radially inward as the outer sleeve of the knobassembly moves relative to the inner sleeve of the knob assembly so thatthe finger secures the rod reducer to the pedicle screw assembly.

In some embodiments, the finger may be configured to bias radiallyoutward when the outer sleeve of the knob assembly is spaced from thefinger so that the rod reducer can separate from the pedicle screwassembly.

According to another aspect, the present disclosure is directed to asurgical system for manipulating a spinal bone. The surgical systemincludes a set screw and a first pedicle screw including a screw and ahousing mounted to the screw. The screw is configured to secure thehousing to spinal bone. The housing includes an internally threadedsurface that defines a rod-receiving passage. The internally threadedsurface is configured to receive the set screw and the rod-receivingpassage is configured to receive a spinal rod.

The surgical system also includes a compression and distractioninstrument configured to generate compressive or distractive forces anda first driving tool engageable with the compression and distractioninstrument to receive compressive or distractive forces therefrom. Thefirst driving tool is configured to rotate the set screw into thehousing of the pedicle screw to partially lock the spinal rod in thehousing of the first pedicle screw. The first driving tool is configuredto impart compressive or distractive forces generated by the compressionand distraction instrument to spinal bone while the spinal rod ispartially locked in the housing. The first driving tool is configured torotate the set screw relative to the housing of the first pedicle screwto fully lock the spinal rod in the housing while the compressive ordistractive forces are imparted from the first driving tool to spinalbone.

In embodiments, an extension assembly may be coupled to the firstpedicle screw housing by a frangible member and the first driving toolmay be advanceable through the extension assembly to rotate the setscrew.

In certain embodiments, a second pedicle screw may be configured to beinserted into a second spinal bone and to receive the spinal rod thereinsuch that the first and second pedicle screws are configured to supportthe spinal rod across different spinal bones.

In embodiments, a second driving tool may be configured to be insertedinto the second pedicle screw while the first driving tool is receivedwithin the first pedicle screw.

In some embodiments, a fulcrum may be provided and may include a bodydefining apertures. One or both of the first or second driving tools isreceivable through one or more of the apertures to enable the body ofthe fulcrum to support one or both of the first or second driving toolsrelative to a respective one of the first or second pedicle screws.

In certain embodiments, the compression and distraction instrument mayinclude a dial, a first body, and a second body disposed on the dial.The second body may be movable on the dial relative to the first body togenerate compressive or distractive forces.

In embodiments, the first body and the second body of the compressionand distraction instrument may be engageable with the first and seconddriving tools, respectively. As the second body moves relative to thefirst body, the compression and distraction instrument may enable thefirst and second driving tools to move a first portion of the spinalbone relative to a second portion of the spinal bone.

According to another aspect, the present disclosure is directed to asurgical system for installing a set screw into a pedicle screwassembly. The pedicle screw assembly includes a screw securable to aspinal bone, a pedicle screw housing mounted to the screw, and anextension assembly coupled to the pedicle screw housing by a frangiblemember. The pedicle screw housing includes an internally threadedsurface that defines a rod-receiving recess. The internally threadedsurface is configured to receive the set screw and the rod-receivingpassage is configured to receive a spinal rod.

The surgical system further includes a support sleeve mountable to thepedicle screw assembly. The support sleeve is configured to inhibit thefrangible member from breaking during rotation of the set screw into thepedicle screw housing. The support sleeve includes a recessed portionconfigured for engagement with an anti-torque tool to inhibit rotationof the support sleeve and the pedicle screw assembly as the set screw isrotated into the pedicle screw housing.

In accordance with another aspect of the present disclosure, there isprovided a method of surgery including mounting a pedicle screw assemblyto a vertebra, mounting a rod reducer on the pedicle screw assembly,placing a spinal rod adjacent a head assembly of the pedicle screwassembly, reducing the spinal rod into a rod-receiving passage of thepedicle screw assembly; and manipulating the rod reducer to breakfrangible members of the head assembly of the pedicle screw assembly inorder to separate the head assembly from an extension assembly of thepedicle screw assembly. In particular, the pedicle screw assemblyincludes the head assembly, a screw extending distally from the headassembly, and the extension assembly extending proximally from the headassembly.

In an embodiment, mounting the rod reducer includes positioning the rodreducer over a proximal portion of the pedicle screw assembly.

In another embodiment, mounting the rod reducer includes engaginggripping fingers of the rod reducer with grooves defined in theextension assembly.

Other aspects, features, and advantages will be apparent from thedescription, the drawings, and the claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the disclosureand, together with a general description of the disclosure given above,and the detailed description of the embodiment(s) given below, serve toexplain the principles of the disclosure, wherein:

FIG. 1 is a front view of an embodiment of a pedicle screw assembly inaccordance with the present disclosure;

FIG. 2 is an enlarged, longitudinal, cross-sectional view of theindicated area of detail of FIG. 1;

FIG. 3A is a front view of an embodiment of a rod reducer assembly shownin an unreduced position in accordance with the present disclosure;

FIG. 3B is a longitudinal, cross-sectional view of the rod reducerassembly of FIG. 3A;

FIG. 4A is a front view of the embodiment of the rod reducer assembly ofFIG. 3A shown in a reduced position;

FIG. 4B is a longitudinal, cross-sectional view of the rod reducerassembly of FIG. 4A;

FIG. 5 is a front view, with parts separated, of another embodiment of arod reducer assembly in accordance with the present disclosure;

FIG. 6 is a perspective view of a derotation sleeve of the rod reducerassembly of FIG. 5 positioned on a pedicle screw assembly of the rodreducer assembly of FIG. 5;

FIG. 7A is a side view of the derotation sleeve and pedicle screwassembly of FIG. 6;

FIG. 7B is an enlarged view of a locking mechanism of the derotationsleeve of FIGS. 5 and 6 shown in an unlocked position;

FIG. 8A is a cross-sectional view of the derotation sleeve and pediclescrew assembly of FIGS. 6 and 7 and the locking mechanism of FIG. 7Bshown in the unlocked position;

FIG. 8B is an enlarged, longitudinal, cross-sectional view of theindicated area of detail delineated in FIG. 8A;

FIG. 9A is a side view of the derotation sleeve and pedicle screwassembly of FIGS. 5 and 6 with the locking mechanism of FIG. 7B shown ina locked position;

FIG. 9B is an enlarged view of the indicated area of detail delineatedin FIG. 9A;

FIG. 10A is a longitudinal, cross-sectional view of the derotationsleeve and pedicle screw assembly of FIGS. 5 and 6 with the lockingmechanism of FIG. 7B shown in the locked position;

FIG. 10B is an enlarged view of the indicated area of detail delineatedin FIG. 10A;

FIG. 11A is a front view of the rod reducer assembly of FIG. 5 with arod reducer of the rod reducer assembly shown in an unreduced position;

FIG. 11B is a longitudinal, cross-sectional view of the rod reducerassembly of FIG. 5, as depicted in FIG. 11A;

FIG. 12A is a front view of the rod reducer assembly of FIG. 5 shown ina reduced position;

FIG. 12B is a longitudinal, cross-sectional view of the rod reducerassembly of FIG. 5, as depicted in FIG. 12A;

FIG. 13 is a front view, with parts separated, of another embodiment ofa rod reducer assembly in accordance with the present disclosure;

FIG. 14 is a perspective view of the rod reducer assembly of FIG. 13with a knob thereof shown unapproximated from a central shaft thereof;

FIG. 15A is a front view of the rod reducer assembly of FIG. 13, asdepicted in FIG. 14, with the rod reducer assembly shown supporting aspinal rod and in an unlocked and unreduced position;

FIG. 15B is a longitudinal, cross-sectional view of the rod reducerassembly of FIG. 13, as depicted in FIG. 15A;

FIG. 16 is a perspective view of the rod reducer assembly of FIG. 13shown in a locked position with the knob and central shaft thereofapproximated with one another;

FIG. 17A is a front view of the rod reducer assembly of FIG. 13, asdepicted in FIG. 16;

FIG. 17B is a longitudinal, cross-sectional view of the rod reducerassembly of FIG. 13, as depicted in FIG. 17A;

FIG. 18 is a perspective view of the rod reducer assembly of FIG. 13shown in a locked and reduced position;

FIG. 19A is a front view of the rod reducer assembly of FIG. 13, asdepicted in FIG. 18;

FIG. 19B is a longitudinal, cross-sectional view of the rod reducerassembly of FIG. 13, as depicted in FIG. 19A;

FIG. 20A is perspective view of a surgical system including adistraction and compression instrument with the distraction andcompression instrument shown coupled to the surgical system in adistraction mode in accordance with the present disclosure;

FIG. 20B is an enlarged view of the indicated area of detail delineatedin FIG. 20A;

FIG. 21 is a perspective view of the surgical system of FIG. 20A withthe distraction and compression instrument shown coupled to the surgicalsystem in a compression mode;

FIG. 22 is a perspective view of another embodiment of a surgical systemin accordance with the present disclosure;

FIG. 23A is a front view of a surgical system in accordance with anotherembodiment of the present disclosure;

FIG. 23B is a longitudinal, cross-sectional view of the surgical systemof FIG. 23A;

FIG. 24A is an enlarged side view of a sleeve of the surgical system ofFIG. 23A;

FIG. 24B is a front, longitudinal, cross-sectional view of the sleeve ofFIG. 24A;

FIG. 25 is an enlarged, longitudinal, cross-sectional view of theindicated area of detail delineated in FIG. 23B; and

FIG. 26 is a perspective view of an anti-torque tool of the surgicalsystem of FIG. 23A.

DETAILED DESCRIPTION

Embodiments of the presently disclosed devices are described in detailwith reference to the drawings, in which like reference numeralsdesignate identical or corresponding elements in each of the severalviews. As used herein, the term “distal” or “leading” refers to thatportion of the device that is farther from the user, while the term“proximal” or “trailing” refers to that portion of the device that iscloser to the user. In addition, the term “cephalad” is known toindicate a direction toward a patient's head, whereas the term “caudad”indicates a direction toward the patient's feet. Further still, the term“lateral” is understood to indicate a direction toward a side of thebody of the patient, i.e., away from the middle of the body of thepatient. The term “posterior” indicates a direction toward the patient'sback, and the term “anterior” indicates a direction toward the patient'sfront. As used herein, the term “clinician” refers to a doctor, nurse,or other care provider and may include support personnel. In thefollowing description, well-known functions or constructions are notdescribed in detail to avoid obscuring the present disclosure inunnecessary detail.

With reference to FIGS. 1-3B, a rod reducer assembly is shown andgenerally designated as 200. The rod reducer assembly 200 defines alongitudinal axis “A1-A1” and includes a pedicle screw assembly 100 anda rod reducer 202. The rod reducer 202 is positionable on the pediclescrew assembly 100 and configured to reduce the spinal rod “R” into apedicle screw housing 120 of the pedicle screw assembly 100. For adetailed description of a similar rod reducer, reference can be made toU.S. Pat. App. Pub. No. 2013/0046345, the entire contents of which areincorporated by reference herein. With particular reference to FIGS. 1and 2, one embodiment of a pedicle screw assembly 100 defines alongitudinal axis “L-L” and includes a pedicle screw 110, a pediclescrew housing 120 supported on a proximal or trailing end of the pediclescrew 110, a tab assembly 130 extending proximally from the pediclescrew housing 120, an extension assembly 140 coupled to the tab assembly130 and extending proximally therefrom, and a head assembly 150 coupledto a proximal end of the extension assembly 140.

The pedicle screw 110 of the pedicle screw assembly 100 has a threadedshank 110 a and a head 110 b supported on a proximal portion of thethreaded shank 110 a. The head 110 b defines a drive recess 110 c, whichmay be any suitable shape such as hexolobular or the like, that isconfigured to selectively receive a drive tool such as a screwdriver,e.g., driver 520 (FIG. 20A), to rotate the threaded shank 110 a of thepedicle screw 110 into bone.

The pedicle screw housing 120 of the pedicle screw assembly 100 isU-shaped and includes a pair of wings or flanges 122 a, 122 b thatdefines a U-shaped rod-receiving passage 124 therethrough at a proximalend of the pedicle screw housing 120. The pair of flanges 122 a, 122 bdefines a threaded internal surface 124 a that is configured tothreadably receive a set screw “S” (FIG. 20B) therein to engage andsecure a spinal rod “R” (shown in phantom in FIG. 2) within the pediclescrew housing 120. The set screw “S” may be advanced into engagementwith the spinal rod “R” via a rod inserter or driver, e.g., driver 520(FIG. 20B). For a more detailed description of spinal rod insertiondevices, reference can be made to, for example, InternationalApplication No. PCT/US16/46523, filed Aug. 11, 2016, the entire contentsof which are incorporated by reference herein. The pedicle screw housing120 further defines a concave recess 126 in a distal end thereof thatreceives the head 110 b of the pedicle screw 110.

With particular reference to FIG. 2, the pedicle screw assembly 100further includes an anvil 128 received within the pedicle screw housing120. The anvil 128 defines a distal recess 128 a that receives theproximal end of the head 110 b of the pedicle screw 110, while the head110 b is disposed within the concave recess 126 of the pedicle screwhousing 120. The anvil 128 further defines a saddle 128 b on a proximalend thereof that supports the spinal rod “R” thereon. For a moredetailed description of similar pedicle screw assemblies, reference canbe made, for example, to U.S. Pat. No. 8,882,817, the entire contents ofwhich are incorporated by reference herein.

The tab assembly 130 of the pedicle screw assembly 100 includes a pairof tabs 132, 134, that may be disposed in mirrored relation with oneanother. The tab 132 defines a recess 132 a and includes a frangiblemember 132 b secured to the flange 122 a at a distal end of the tab 132.The tab 134 defines a recess 134 a and includes a frangible member 134 bsecured to flange 122 b at a distal end of the tab 134. The frangiblemembers 132 b, 134 b may be integrally and/or monolithically formed withrespective flanges 122 a, 122 b. The frangible members 132 b, 134 b maybe configured to break upon application of a threshold force thereto(e.g., twisting, bending, tensile, and/or shear forces) to enable thetabs 132, 134 to separate from the flanges 122 a, 122 b. As used herein,the term “break” (or its equivalent) refers to rupturing, dividing,tearing, fracturing, splitting, and/or the like.

With continued reference to FIG. 2, the extension assembly 140 of thepedicle screw assembly 100 includes a pair of extensions 142, 144coupled to the tabs 132, 134 of the pedicle screw assembly 100 by rings136. More specifically, each of the pair of extensions 142, 144 definesa recess 146 in distal end portion thereof to receive one of the tabs132, 134 of the tab assembly 130 and one of the rings 136 therein,respectively. A protuberance 148 extends from the recess 146 and isreceivable through an opening 136 a defined by the ring 136. Using anyknown securement technique such as welding, friction-fit, adhesion orthe like, the rings 136 are secured about the protuberances 148 andwithin the recesses 146 of the extension assembly 140 and the recesses132 a, 134 a of the tabs 132, 134, respectively, to couple the extensionassembly 140 to the tabs 132, 134. The extension assembly 140 furtherincludes an internal threaded surface 149 in vertical registration withthe threaded internal surface 124 a of the pedicle screw housing 120.The internal threaded surface 149 threadably receives the set screw “S”(FIG. 20B) and facilitates threaded reception of the set screw “S” intothe pedicle screw housing 120 via the threaded internal surface 124 a ofthe pedicle screw housing 120. Proximal portions of each of the pair ofextensions 142, 144 define grooves 160 a and 160 b (FIG. 1) that areconfigured to facilitate selective attachment to various rod reducinginstruments, as will be described in detail below. The grooves 160 a,160 b may have any suitable shape such as circular and/or noncircular.The grooves 160 a, 160 may be elongated in a direction transverse to thelongitudinal axis “L-L” of the pedicle screw assembly 100. The proximalportions of each of the extensions 142, 144 further include outercamming surfaces 162 a, 162 b.

With brief reference back to FIG. 1, the head assembly 150 of thepedicle screw assembly 100 defines a recess 152 having an invertedU-shape that separates a pair of arms 154 a, 154 b of the head assembly150. Distal ends of the pair of arms 154 a, 154 b are coupled toproximal ends of the extensions 142, 144 of the extension assembly 140by the frangible members 156 a, 156 b. Similar to the frangible members132 b, 134 b of the tab assembly 130, the frangible members 156 a, 156 bof the head assembly 150 are configured to break upon application of athreshold force thereto to separate the head assembly 150 from theextension assembly 140 as desired, for example, with a pair of pliers asdetailed in International Application No. PCT/US16/46523 incorporatedherein by reference above.

With particular reference to FIGS. 3A and 3B, the rod reducer 202 of therod reducer assembly 200 has a knob or cap 204 having a distal portionthat is rotatably connected to a proximal portion of a sleeve assembly206 of the rod reducer 202. The cap 204 of the rod reducer 202 includesan outer surface 204 a and a threaded internal surface 204 b thatdefines a central opening 204 c through the cap 204. The outer surface204 a of the cap 204 further includes a drive surface 204 d configuredto impart axial drive force, as indicated by arrows “Y” (FIG. 4A), ontothe sleeve assembly 206 in response to rotation of the cap 204, asindicated by arrows “Z,” about the longitudinal axis “A1-A1” (e.g.,clockwise and/or counterclockwise) of the rod reducer assembly 200relative to the sleeve assembly 206.

The sleeve assembly 206 of the rod reducer assembly 200 includes aninner sleeve 208, an outer sleeve 210 and a retaining ring 212 securedto an inner surface of the outer sleeve 210 adjacent to the inner sleeve208. The inner sleeve 208 of the sleeve assembly 206 includes a threadedexternal surface 208 a on a proximal end portion thereof and grippingfingers 208 b, 208 c on a distal end portion thereof. The grippingfingers 208 b, 208 c of the inner sleeve 208 may be in the form ofhooks. The threaded external surface 208 a of the inner sleeve 208 isconfigured to threadably engage the threaded internal surface 204 b ofthe cap 204 to facilitate rotation of the cap 204 relative to the sleeveassembly 206. The gripping fingers 208 b, 208 c of the inner sleeve 208are configured to engage the grooves 160 a and 160 b of the pediclescrew assembly 100 to rotationally fix the inner sleeve 208 to thepedicle screw assembly 100, thereby fixing the rod reducer 202 to thepedicle screw assembly 100. The gripping fingers 208 b, 208 c may beflexible to facilitate a snap-fit engagement into the grooves 160 a and160 b of the pedicle screw assembly 100.

The outer sleeve 210 of the sleeve assembly 206 is in contactingrelation with the drive surface 204 d of the cap 204 and positioned tosurround the inner sleeve 208 and the distal portion of the cap 204. Theouter sleeve 210 includes a proximal portion 210 a and a distal portion210 b. The distal portion 210 b of the outer sleeve 210 defines one ormore rod-engaging recesses 210 c configured to engage the spinal rod“R.” Each of the rod-engaging recesses 210 c may have an invertedU-shaped configuration. The proximal portion 210 a of the outer sleeve210 is positioned to receive the distal portion of the cap 204 to enablethe cap 204 to rotate relative to the outer sleeve 210. The outer sleeve210 further defines longitudinal slots 210 d, 210 e that receive thegripping fingers 208 b, 208 c of the inner sleeve 208 therein. Thelongitudinal slots 210 d, 210 e are positioned to slide along thegripping fingers 208 b, 208 c of the outer sleeve 210 to enable theouter sleeve 210 to slide axially relative to the inner sleeve 208 inresponse to rotation of the cap 204 relative to the sleeve assembly 206.

In operation, the pedicle screw assembly 100 of the rod reducer assembly200 is mounted to a vertebra (e.g., screwed in to the vertebra) of aspine (not shown) so that the rod reducer 202 of the rod reducerassembly 200 can be mounted on the pedicle screw assembly 100 as seen inFIGS. 3A and 3B. To mount the rod reducer 202 to the pedicle screwassembly 100, the rod reducer 202 is positioned over the proximalportion of the pedicle screw assembly 100 and advanced distally alongthe pedicle screw assembly 100. As the rod reducer 202 is advanceddistally, the gripping fingers 208 b, 208 c of the rod reducer 202engage and cam along the camming surfaces 162 a, 162 b of the extensionassembly 140 of the pedicle screw assembly 100. The camming surfaces 162a, 162 b of the pedicle screw assembly 100 are configured to urge orflex the gripping fingers 208 b, 208 c of the rod reducer 202 radiallyoutward as the gripping fingers 208 b, 208 c are advanced distallytherealong until the gripping fingers 208 b, 208 c of the of the rodreducer 202 snap radially inward and into the grooves 160 a, 160 b ofthe extension assembly 140 of the pedicle screw assembly 100. Engagementof the gripping fingers 208 b, 208 c of the rod reducer 202 and thegrooves 160 a, 160 b of the extension assembly 140 of the pedicle screwassembly 100 locks the rod reducer 202 onto the pedicle screw assembly100. With the gripping fingers 208 b, 208 c of the rod reducer 202secured to the grooves 160 a, 160 b of the extension assembly 140, theinner sleeve 208 of the rod reducer 202 is axially fixed onto theproximal portion of the pedicle screw assembly 100.

Referring now to FIGS. 1-4B, with the spinal rod “R” positioned withinthe rod-receiving passage 124 of the pedicle screw assembly 100, and therod reducer 202 locked onto the pedicle screw assembly 100, the cap 204of the rod reducer 202 is rotatable (e.g., clockwise and/orcounterclockwise) relative to sleeve assembly 206 of the rod reducer 202to impart axial force onto the sleeve assembly 206 through the drivesurface 204 d of the cap 204. In particular, rotation of the cap 204(e.g., clockwise and/or counterclockwise) relative to the sleeveassembly 206, as indicated by arrow “Z,” axially moves the outer sleeve210 of the sleeve assembly 206, as indicated by arrow “Y,” along thelongitudinal axis “A1-A1” of the rod reducer assembly 200, and relativeto the inner sleeve 208 of the sleeve assembly 206 (and relative to thepedicle screw assembly 100), from a proximal or unreduced position(FIGS. 3A and 3B) to a distal or reduced position (FIGS. 4A and 4B).

As the outer sleeve 210 of the rod reducer 202 is advanced distallyrelative to the pedicle screw assembly 100, the rod-engaging recesses210 c of the outer sleeve 210 engage the spinal rod “R” to reduce thespinal rod “R” into the pedicle screw housing 120 of pedicle screwassembly 100 as the outer sleeve 210 moves from the unreduced positionto the reduced position.

In the reduced position of the outer sleeve 210 of the rod reducer 200,the outer sleeve 210 supports or stabilizes the frangible members 132 b,134 b, 156 a, 156 b of the pedicle screw assembly 100 (see FIGS. 1 and2) so that the rod reducer assembly 200 can be manipulated (e.g., in oneor more caudad, cephalad, posterior, anterior, and/or lateraldirections) to selectively position and/or reposition the rod reducerassembly 200, the spinal column, and/or portions of the spinal column asdesired.

By virtue of the structural arrangement of one or more of the componentsof the rod reducer assembly 200 and/or the rigidity thereof, the rodreducer assembly 200 is configured to reinforce the pedicle screwassembly 100, extension assembly 140, the tab assembly 130, and/or thehead assembly 150 by limiting forces (e.g., twisting, bending, flexing,tensile, and/or shear forces) from being applied (e.g. directly) to thefrangible members 132 b, 134 b of the pedicle screw assembly 100 and/orto the frangible members 156 a, 156 b of the head assembly 150 (e.g., inone or more caudad, cephalad, posterior, anterior, and/or lateraldirections). Instead, the rod reducer assembly 200 and/or componentsthereof, are configured to absorb these forces and inhibit the tabs 132,134 of the tab assembly 130 from prematurely separating from the flanges122 a, 122 b of the pedicle screw housing 120 and/or the head assembly150 from prematurely separating from the extension assembly 140.

Once the rod reducer assembly 200 is positioned as desired, the cap 204of the rod reducer 202 can be rotated to move the outer sleeve 210 ofthe sleeve assembly 206 of the rod reducer 202 to a proximal position(see, e.g., FIG. 3A) that is proximal of the frangible members 132 b,134 b of the pedicle screw assembly 100. In such a proximal position,lateral movement of the rod reducer 202 to a breaking threshold angle“a” (e.g., from about 1 degree to about 20 degrees) relative to thepedicle screw assembly 100 will break the frangible members 132 b, 134 band separate the rod reducer 202, the head assembly 150, the extensionassembly 140, and the tab assembly 130 from the pedicle screw housing120 of the pedicle screw assembly 100.

Alternatively, to separate the rod reducer 202 from the pedicle screwassembly 100 without breaking the frangible members 132 b, 134 b of thepedicle screw assembly 100, the rod reducer 202 can be rotated relativeto the pedicle screw assembly 100 while the rod reducer 202 is disposedin the reduced position. In the reduced position, the fingers 208 b, 208c of the rod reducer 202 are configured to cam out of the grooves 160 a,160 b of the extension assembly 140 as the rod reducer 202 is rotatedabout the longitudinal axis “L-L” of the pedicle screw assembly 100 andrelative to the pedicle screw assembly 100, as indicated by arrows “ZZ”(FIG. 4A). Once the rod reducer 202 is separated from the pedicle screwassembly 100, the head assembly 150, the extension assembly 140, and/orthe tab assembly 130 of the pedicle screw assembly 100 can then beseparated or otherwise broken from the pedicle screw housing 120 of thepedicle screw assembly 100 using various instruments (not shown) such asthose described in International Application No. PCT/US16/46523, entirecontents of which are incorporated by reference herein.

With reference to FIGS. 1, 2, and 5, a rod reducer assembly inaccordance with another embodiment of the present disclosure is shownand generally designated as 300. The rod reducer assembly 300 defines alongitudinal axis “A2-A2” and generally includes the pedicle screwassembly 100, a rod reducer 310, and a derotation sleeve 320. The rodreducer 310 may be used to reduce a spinal rod “R” into the pediclescrew housing 120 of the pedicle screw assembly 100 and the derotationsleeve 320 may be used to manipulate the spine while inhibiting thefrangible members 132 b, 134 b and 156 a, 156 b of the tab and headassemblies 130, 150 of the pedicle screw assembly 100, respectively,from breaking, similar to that described above with respect to the rodreducer assembly 200.

With reference now to FIGS. 6-10B, the derotation sleeve 320 of the rodreducer assembly 300 includes a knob 321, an upper shaft portion 322extending distally from the knob 321, a lower shaft portion 323extending distally from the upper shaft portion 322, and a lockingmechanism 330 supported between the upper and lower shaft portions 322,323 for selectively locking the upper and lower shaft portions 322, 323together.

The knob 321 of the derotation sleeve 320 includes a first portion 3210and a second portion 3212 that are pinned together by pins 3214. Thefirst portion 3210 of the knob 321 includes an internal threaded surface321 a configured to threadably receive the rod reducer 310 (FIG. 5). Thesecond portion 3212 of the knob 321 includes and an internal threadedsurface 321 b configured to threadably engage the upper shaft portion322 of the derotation sleeve 320. The second portion 3212 of the knob321 also includes an outer surface 3212 a that defines a slot 3212 btherein. The second portion 3212 of the knob 321 is rotatably connectedto the upper shaft portion 322 by a retaining ring 321 c. The retainingring 321 c is positioned between the knob 321 of the derotation sleeve320 and the upper shaft portion 322 of the derotation sleeve 320 toenable the knob 321 to rotate about the upper shaft portion 322 (e.g.,clockwise and/or counterclockwise), as indicated by arrows “X” (FIG. 6).

The upper shaft portion 322 of the derotation sleeve 320 includes asleeve assembly 3222 having an outer sleeve 3224 and an inner sleeve3226. The outer sleeve 3224 includes an inner surface 3224 a defining aslot 3224 b that receives the retaining ring 321 c therein. The outersleeve 3224 is positioned to move axially, as indicated arrows “W” (FIG.6), along the longitudinal axis “A2-A2” of the rod reducer assembly 300and relative to the inner sleeve 3226 in response to rotation of theknob 321 of the derotation sleeve 320. The outer sleeve 3224 furtherincludes teeth 331 that extend distally from the outer sleeve 3224.

The inner sleeve 3226 of the sleeve assembly 3222 includes threads 322 con a proximal outer surface thereof. The threads 322 c (FIG. 10B) of theinner sleeve 3226 are disposed in threaded engagement with the internalthreaded surface 321 b of the knob 321. The inner sleeve 3226 of sleeveassembly 3222 further includes fingers 322 a, 322 b that are selectivelyengagable with the grooves 160 a, 160 b of the extension assembly 140 ofthe pedicle screw assembly 100, similar to the fingers 208 b, 208 c ofthe rod reducer assembly 200 described above. The inner sleeve 3226 ofthe sleeve assembly 3222 includes a distal portion 3226 a that isreceived within a proximal portion of the lower shaft portion 323 of thederotation sleeve 320. The inner sleeve 3226 of the sleeve assembly 3222is selectively rotatably connected to the lower shaft portion 323 by aretaining ring 322 d. The retaining ring 322 d is configured to enablethe upper shaft portion 322 of the derotation sleeve 320 to rotate aboutthe longitudinal axis “A2-A2” (e.g., clockwise and/or counterclockwise)relative to the lower shaft portion 323, as indicated by arrows “V”(FIG. 7A), when the locking mechanism 330 is disposed in an unlockedposition (FIG. 7A) for rotatably separating the fingers 322 a, 322 b ofthe sleeve assembly 3222 from the grooves 160 a, 160 b of extensionassembly 140 of pedicle screw assembly 100 (see FIGS. 8A and 8B).

The lower shaft portion 323 of the derotation sleeve 320 definesrecesses 332 at a proximal end thereof configured for engagement withthe plurality of teeth 331 of the upper shaft portion 322 of thederotation sleeve 320. The lower shaft portion 323 further includesfirst and second legs 324 a, 324 b which are positionable about thepedicle screw assembly 100 adjacent to the frangible members 132 b, 134b to stabilize and/or support the frangible members 132 b, 134 b forinhibiting premature breaking of the frangible members 132 b, 134 bduring manipulation and/or derotation of the spinal column with thederotation sleeve 320 and the pedicle screw assembly 100 coupledtogether.

By virtue of the structural arrangement of one or more of the componentsof the rod reducer assembly 300 and/or the rigidity thereof, the rodreducer assembly 300 is configured to reinforce the pedicle screwassembly 100, extension assembly 140, the tab assembly 130, and/or thehead assembly 150 by limiting forces (e.g., twisting, bending, flexing,tensile, and/or shear forces) from being applied (e.g. directly) to thefrangible members 132 b, 134 b of the pedicle screw assembly 100 and/orto the frangible members 156 a, 156 b of the head assembly 150 (e.g., inone or more caudad, cephalad, posterior, anterior, and/or lateraldirections). Instead, the rod reducer assembly 300 and/or componentsthereof, are configured to absorb these forces and inhibit the tabs 132,134 of the tab assembly 130 from prematurely separating from the flanges122 a, 122 b of the pedicle screw housing 120 and/or the head assembly150 from prematurely separating from the extension assembly 140.

With reference to FIG. 7B, the locking mechanism 330 of the derotationassembly 320 includes the teeth 331 of the upper shaft portion 322 ofthe derotation assembly 300 and the recesses 332 of the lower shaftportion 323 of the derotation assembly 300. The locking mechanism 330 ispositionable between an unlocked position (FIG. 7B) and a lockedposition (FIG. 9B). In the unlocked position of the locking mechanism330, the teeth 331 of the locking mechanism 330 are spaced apart fromthe recesses 332 of the locking mechanism 330 by a gap “G” (FIG. 8B) sothat the upper shaft portion 322 can rotate relative to the lower shaftportion 323 to enable the derotation assembly 300 to separate from thepedicle screw assembly 100. In the locked position of the lockingmechanism 330, the teeth 331 and the recesses 332 are engaged so thatthe fingers 322 a, 322 b (FIG. 8B) of the sleeve assembly 3222 remainengaged within the grooves 160 a, 160 b of extension assembly 140 andthe derotation assembly 320 and the pedicle screw assembly 100 move(e.g., rotate) together, as indicated by arrows “U” (FIG. 9A), forexample, to derotate the spinal column.

In use, and with reference to FIGS. 1, 2, and FIGS. 6-10B, thederotation sleeve 320 of the rod reducer assembly 300 is mounted overthe pedicle screw assembly 100 and advanced distally along the pediclescrew assembly 100 until the fingers 322 a, 322 b of upper shaft portion322 of the derotation sleeve 320 engage (e.g., “snap” into) or lock intothe grooves 160 a, 160 b of the extension assembly 140 of the pediclescrew assembly 100 (FIG. 8B). Initially, the locking mechanism 330 isdisposed in the unlocked position with the teeth 331 of upper shaftportion 322 of the derotation sleeve 320 disengaged and spaced from therecesses 332 of the lower shaft portion 323 by the gap “G”.

In order to position the locking mechanism 330 of the derotation sleeve320 into the locked position, a rotational (e.g., clockwise and/orcounterclockwise) force is applied to the knob 321 of the derotationsleeve 320, as indicated by arrow “X,” (FIG. 6) so that the threads 321b of the knob 321 engage with the threads 322 c of the upper shaftportion 322 of the derotation sleeve 320. As the knob 321 rotates, thethreaded engagement between the knob 321 and the upper shaft portion 322moves the knob 321 distally along the threads 322 c of the upper shaftportion 322, as indicated by arrow “W” (see FIGS. 6 and 8B). The distalmovement of the knob 321 relative to the upper shaft portion 322 causesthe first portion 3210 of the upper shaft portion 322 to move distallyuntil the teeth 331 (FIG. 7B) of the locking mechanism 330 engage withthe recesses 332 of the locking mechanism 330 (FIG. 9B). Once the teeth331 are fully seated within the recesses 332, the locking mechanism 330is disposed in the locked position such that the upper and lower shaftportions 322, 324 are locked together with the gap “G” (FIG. 8B)eliminated or substantially reduced as seen in at least FIGS. 9A, 9B,10A, and 10B.

With the locking mechanism 330 of the derotation sleeve 330 disposed inthe locked position on the pedicle screw assembly 100, the derotationsleeve 320 and the pedicle screw assembly 100 can move together tomanipulate the spine as desired, for example, to derotate the spineand/or to correct a spinal deformity. More particularly, the derotationsleeve 330 is positioned on the pedicle screw assembly 100 so that thefrangible members 132 b, 134 b, 156 a, 156 b of the pedicle screwassembly 100 are stabilized to inhibit the frangible members 132 b, 134b, 156 a, 156 b from breaking during derotation of the spine. For a moredetailed description of related spinal derotation devices and methods,reference can be made, for example, to U.S. Pat. No. 8,956,360, theentire contents of which are incorporated by reference herein. Referencecan also be made to International Application No. PCT/US16/46523, theentire contents of which are also incorporated by reference herein.

When a clinician desires to reduce a spinal rod “R” into the pediclescrew assembly 100, the clinician can insert the spinal rod “R” betweenthe first and second legs 324 a, 324 b of derotation sleeve 320 and theextensions 142, 144 (FIG. 1) of the extension assembly 140 of thepedicle screw assembly 100. The rod reducer 310 may be mounted to thederotation sleeve 320 while the derotation sleeve 320 is mounted on thepedicle screw assembly 100 to reduce the spinal rod “R” into the saddle128 b (FIG. 2) of the pedicle screw assembly 100.

As seen in FIGS. 5, 11A, 11B, 12A, and 12B, the rod reducer 310 of therod reducer assembly 300 includes a cap 310 a that is rotatably coupledto a sleeve assembly 310 b, as indicated by arrows “Q” (FIG. 11A), by aretaining ring 310 c. The cap 310 a of the rod reducer 310 includes adistal portion with a threaded outer surface 311 a and a proximalgripping portion 311 b.

The sleeve assembly 310 b includes an outer sleeve 312 that is rotatablycoupled to an inner sleeve 313, as indicated by arrow “T” (FIG. 11A), toenable the inner sleeve 313 to advance axially relative to the outersleeve 312, as indicated by arrow “N,” between a proximal or unreducedposition (FIG. 11A) and a distal or reduced position (FIG. 12A). Theouter sleeve 312 includes an internal threaded surface 312 a. The innersleeve 313 includes a first arm 313 a and a second arm 313 b that arecoupled by a nut 313 c having an inner surface 313 d and a threadedouter surface 313 e. The threaded outer surface 313 e of the nut 313 cis threadably engagable with internal threaded surface 312 a of theouter sleeve 312 to enable the outer sleeve 312 to rotate about thelongitudinal axis “A2-A2” of the rod reducer assembly 300 and relativeto the inner sleeve 313 thereof. The first and second arms 313 a, 313 bof the inner sleeve 313 extend distally from opposite sides of the nut313 c to rod-engaging recesses 314 a, 314 b, respectively. Therod-engaging recesses 314 a, 314 b of the inner sleeve 313 may includeinverted U-shaped or arched configurations.

In use, the rod reducer 310 of the rod reducer assembly 300 is mountedover the derotation sleeve 320 so that the distal portion of the cap 310a of the rod reducer 310 is threadably received in the proximal end ofthe knob 321 of the derotation sleeve 320 as seen in FIGS. 11A and 11B.Specifically, the threaded outer surface 311 a of the cap 310 a of therod reducer 310 threadably engages with the internal threaded surface321 a of the knob 321 of the derotation sleeve 320 to mount the rodreducer 310 to the derotation sleeve 320 and the pedicle screw assembly100.

Once the rod reducer 310 is threadably mounted onto the derotationsleeve 320, the outer sleeve 312 of the rod reducer 310 can be rotatedrelative to the inner sleeve 313, as indicated by arrows “T,” to drivethe first and second arms 313 a, 313 b of the inner sleeve 313 distallyfrom the unreduced position (FIGS. 11A and 11B) to the reduced position(FIGS. 12A and 12B) and reduce the spinal rod “R” into the saddle 128 b(FIG. 2) of the pedicle screw assembly 100.

With the frangible members 132 b, 134 b, 156 a, 156 b of the pediclescrew assembly 100 (see FIGS. 1 and 2) supported/stabilized by thederotation sleeve 320, the entire rod reducer assembly 300 can likewisebe manipulated to selectively position and/or reposition the rod reducerassembly 300, the spinal column, and/or portions of the spinal column asdesired. It should be appreciated that derotation of the spine andcompression and distraction of vertebrae may be performed with, orwithout, the rod reducer 310 mounted to the derotation sleeve 320.

The rod reducer 310 may be removed from the derotation sleeve 320 byunthreading of the cap 310 a from the knob 321 of the derotation sleeve320. The derotation sleeve 320 may be removed by unthreading the knob321 of the derotation sleeve 320 from the upper shaft portion 322 of thederotation sleeve 320 so that the teeth 331 of to the locking mechanism330 of the derotation sleeve 320 disengage from the recesses 332 of thelocking mechanism 330 to unlock the locking mechanism 330 and separateand upper and lower shaft portions 322, 323. With the locking mechanism330 unlocked, the upper shaft portion 322 can be rotated relative to thelower shaft portion 323 so that the fingers 322 a, 322 b of the uppershaft portion 322 rotatably cam out of the grooves 160 a, 160 b of theextension assembly 140 and the derotation sleeve 320 separates from thepedicle screw assembly 100.

Referring now to FIGS. 1, 2, 13 and 14, a rod reducer assembly inaccordance with another embodiment of the present disclosure is shownand generally designated as 400. The rod reducer assembly 400 ispositionable on the pedicle screw assembly 100 and configured to reducethe spinal rod “R” (FIG. 2) into the pedicle screw housing 120 of thepedicle screw assembly 100 and to inhibit the frangible members 132 b,134 b, 156 a, 156 b of the tab and head assemblies 130, 150 of thepedicle screw assembly 100, respectively, from prematurely breakingduring a derotation and/or manipulation of the spine.

By virtue of the structural arrangement of one or more of the componentsof the rod reducer assembly 400 and/or the rigidity thereof, the rodreducer assembly 400 is configured to reinforce the pedicle screwassembly 100, extension assembly 140, the tab assembly 130, and/or thehead assembly 150 by limiting forces (e.g., twisting, bending, flexing,tensile, and/or shear forces) from being applied (e.g. directly) to thefrangible members 132 b, 134 b of the pedicle screw assembly 100 and/orto the frangible members 156 a, 156 b of the head assembly 150 (e.g., inone or more caudad, cephalad, posterior, anterior, and/or lateraldirections). Instead, the rod reducer assembly 400 and/or componentsthereof, are configured to absorb these forces and inhibit the tabs 132,134 of the tab assembly 130 from prematurely separating from the flanges122 a, 122 b of the pedicle screw housing 120 and/or the head assembly150 from prematurely separating from the extension assembly 140.

With reference also to FIGS. 15A, 15B, 16, and 18, the rod reducerassembly 400 defines a longitudinal axis “A3-A3” and generally includesthe pedicle screw assembly 100 and a rod reducer 410. The rod reducer410 includes a knob assembly 412 configured to selectively mount the rodreducer 410 to the pedicle screw assembly 100 and a reduction sleeveassembly 414 coupled to the knob assembly 412 and configured to reducethe spinal rod “R” (FIG. 2) into the pedicle screw assembly 100 whilethe rod reducer 410 is mounted to the pedicle screw assembly 100.

The knob assembly 412 of the rod reducer 410 includes an outer sleeve412 a that defines a threaded internal surface 412 b and an inner sleeve412 c. The outer sleeve 412 a is rotatable (e.g., clockwise and/orcounterclockwise) about the inner sleeve 412 c, as indicated by arrows“H,” and axially movable along the longitudinal axis “A3-A3” between aproximal position (FIG. 15A) and distal position (FIG. 16), as indicatedby arrows “I.” The inner sleeve 412 c is positioned within the outersleeve 412 a and includes a proximal portion 412 d, a central portion412 e, and a distal portion 412 f. The proximal portion 412 d of theinner sleeve 412 c includes a threaded outer surface 412 g thatthreadably engages the threaded internal surface 412 b of the outersleeve 412 a. The central portion 412 e of the inner sleeve 412 cincludes first and second fingers 412 h, 412 i supported on oppositesides of the central portion 412 e. The first and second fingers 412 h,412 i, which may each be in the form of a hook, are biased radiallyoutward and are configured to be received within the grooves 160 a and160 b of the pedicle screw assembly 100. The distal portion 412 f of theinner sleeve 412 c is received within a proximal portion of thereduction sleeve assembly 414 and coupled to the reduction sleeveassembly 414 by a retaining ring 416.

The reduction sleeve assembly 414 of the rod reducer assembly 400includes an outer sleeve 418, a first inner sleeve 420 a coupled to theouter sleeve 418 and configured to reduce the spinal rod “R” in responseto rotation of the outer sleeve 418, and a second inner sleeve 420 bcoupled to the first inner sleeve 420 a and configured to mount to thepedicle screw housing 120 of the pedicle screw assembly 100. The firstand second inner sleeves 420 a, 420 b are positioned within the outersleeve 418. As indicated by arrow “F” (FIG. 15A), the outer sleeve 418is rotatable about the longitudinal axis “A3-A3” relative to the innersleeves 420 a, 420 b. As seen in FIG. 18, and as indicated by arrows“O,” the first inner sleeve 420 a is axially movable along thelongitudinal axis “A3-A3” of the rod reducer assembly 400 relative tothe outer sleeve 418 and the second inner sleeve 420 b between aproximal or unreduced position (FIG. 16) and a distal or reducedposition (FIG. 18). The outer sleeve 418 of the reduction sleeveassembly 414 is rotatably coupled to the distal portion 412 f of theinner sleeve 412 c of the knob assembly 412 by the retaining ring 416.The retaining ring 416 is configured to enable the outer sleeve 418 ofthe reduction sleeve assembly 414 to rotate relative to the inner sleeve412 c of the knob assembly 412 and the first and second inner sleeves420 a, 420 b of the reduction sleeve assembly 414. The outer sleeve 418includes an outer surface 418 a and a threaded inner surface 418 b.

The first inner sleeve 420 a of the reduction sleeve assembly 414 isaxially advanceable along the pedicle screw assembly 100. The firstinner sleeve 420 a has a tubular body 424 having a threaded proximal endportion 424 a and a distal end portion 424 b. The distal end portion 424b (FIG. 19B) of the first inner sleeve 420 a defines a firstrod-engaging recess 424 c on a first side of the tubular body 424 and asecond rod-engaging recess 424 d on a second side of the tubular body424. The first and second recesses 424 c, 424 d are positioned to engagethe spinal rod “R” and may have an inverted U-shaped or archedconfiguration.

The second inner sleeve 420 b has a tubular proximal portion fixedlysupported within the inner sleeve 412 c of the knob assembly 412 and adistal portion having first and second legs 413 a, 413 b that areconfigured to couple to outer side surfaces of the pedicle screw housing120 of the pedicle screw assembly 100 to support the rod reducer 410 onthe pedicle screw assembly 100. The first and second legs 413 a, 413 bdefine a spinal rod passage 413 c configured to slidably receive aspinal rod “R” (FIG. 2) axially therealong.

With reference to FIGS. 13-19B, in use, the rod reducer 410 is mountedover the pedicle screw assembly 100 with the outer sleeve 412 a of theknob assembly 412 of the rod reducer 410 in the proximal position andthe first and second fingers 412 h, 412 i of the knob assembly 412biased radially outward and axially aligned with the grooves 160 a and160 b of the pedicle screw assembly 100. In order to secure the rodreducer 410 to the pedicle screw assembly 100, the outer sleeve 412 a ofthe knob assembly 412 is rotated relative to the inner sleeve 412 c ofthe knob assembly 412 until the outer sleeve 412 a engages the first andsecond fingers 412 h, 412 i of the inner sleeve 412 c of the knobassembly 412. As the outer sleeve 412 a continues to advance distallytoward the distal position of the inner sleeve 412 c, the outer sleeve412 a urges the fingers 412 h, 412 i of the inner sleeve 412 c radiallyinward into the grooves 160 a and 160 b of the pedicle screw assembly100, as indicated by arrows “E” (FIG. 17B). With the fingers 412 h, 412i of the inner sleeve 412 c positioned in the grooves 160 a and 160 b ofthe pedicle screw assembly 100, the rod reducer 410 is locked onto thepedicle screw assembly 100.

Once the rod reducer 410 of the rod reducer assembly 400 is locked ontothe pedicle screw assembly 100 of the rod reducer assembly 400, the rodreducer 410 may be used to manipulate and/or derotate the spine orcorrect a spinal deformity while supporting/stabilizing the frangiblemembers 132 b, 134 b, 156 a, 156 b of the pedicle screw assembly 100.While locked onto the pedicle screw assembly 100, the rod reducer 410 isconfigured to inhibit the frangible members 132 b, 134 b, 156 a, 156 bof the pedicle screw assembly 100 from prematurely breaking during aderotation and/or manipulation procedure.

In order to reduce the spinal rod “R” (FIG. 2) into the pedicle screwhousing 120 of the pedicle screw assembly 100, the outer sleeve 418 ofthe reduction sleeve assembly 414 of the rod reducer assembly 400 isrotated relative to the inner sleeves 420 a, 420 b of the reductionsleeve assembly 414, as indicated by arrows “F” (FIG. 15A). As the outersleeve 418 is rotated, the first inner sleeve 420 a moves distallyrelative to the second inner sleeve 420 b and along the pedicle screwassembly 100 by virtue of the threaded engagement between the firstinner sleeve 420 a and the outer sleeve 418. Distal advancement of thefirst inner sleeve 420 a causes the first and second recesses 424 c, 424d to engage and reduce the spinal rod “R” into the pedicle screw housing120 of the pedicle screw assembly 100. To remove the rod reducer 410 ofthe rod reducer assembly 400 from the pedicle screw assembly 100 of therod reducer assembly 400, the outer sleeve 412 a of the knob assembly412 is rotated to advance the outer sleeve 412 a of the knob assembly412 proximally relative to the inner sleeve 412 c of the knob assembly412 until the fingers 412 h, 412 i of the inner sleeve 412 c areexposed. With the fingers 412 h, 412 i exposed, the fingers 412 h, 412 iare configured to bias radially outward from within the grooves 160 aand 160 b of the pedicle screw assembly 100, as indicated by arrows “C”(FIG. 15B). The rod reducer 410 may then be removed from the pediclescrew assembly 100.

With any of the presently disclosed rod reducers coupled or uncoupled tothe presently disclosed pedicle screw assemblies, a set screw “S” (FIG.20B) may be threaded into the pedicle screw housing 120 of the pediclescrew assembly 100 via the threaded internal surface 124 a of thepedicle screw housing 120 to facilitate seating and/or securement of thespinal rod “R” into the saddle 128 b of the pedicle screw housing 120.

Referring now to FIG. 20A, a surgical system for mounting and/ormanipulating spinal rods “R” and/or pedicle screw assemblies to a spinalcolumn is provided. The surgical system is generally designated as 500.The surgical system 500 may be used to manipulate vertebrae inconjunction with any of the presently disclosed rod reducer assemblies.The surgical system 500 includes a handle 510 selectively attachable toone or more drivers 520 for mounting one or more pedicle screwassemblies 100 to a spine and/or for securing one or more set screws “S”to the one or more pedicle screw assemblies 100. The surgical system 500further includes a fulcrum 530 mountable to the one or more drivers 520for supporting the drivers 520 and a distraction and compressioninstrument 540 selectively engagable with the one or more drivers 520 toapproximate or unapproximate the one or more drivers 520.

The handle 510 of the surgical system 500 includes a gripping portion511 at a proximal end thereof and a mounting sleeve 512 at a distal endthereof for mounting to a proximal end of the driver 520. The driver 520includes an elongated shaft 520 b and a driving bit 521 that extendsdistally from the elongated shaft 520 b. The driver 520 further includesa boss 522 disposed along elongated shaft 520 b.

The fulcrum 530 of the surgical system 500 includes a body 531 definingapertures 531 a. Each of the apertures 531 a is configured to receivethe boss 522 of one of the drivers 520 such that adjacent drivers 520can be positioned adjacent one another.

The distraction and compression instrument 540 of the surgical system500 includes a stationary body 541 a having a wing 542 a extendingtherefrom, and a movable body 541 b having a wing 542 b extendingtherefrom. The stationary and movable body 541 a, 541 b are supported ona dial 545 having teeth 545 a for slidably engaging with movable body541 b as the movable body 541 b moves along the dial 545, as indicatedby arrows “B,” (FIG. 20A) relative to the stationary body 541 a betweenapproximated (FIG. 20A) and unapproximated positions (FIG. 21). Themovable body 541 b includes a driver receiver 543 that is operativelycoupled to the teeth 545 a of the dial 545 and is rotatable, asindicated by arrows “M” (FIG. 20A), to slide the movable body 541 balong the dial 545 between the approximated and unapproximated positionsrelative to the stationary body 541 a. The movable body 541 b furtherincludes a switch 544 that is operable to select between a distractionmode, in which the movable body 541 b moves away or unapproximates fromthe stationary body 541 a as the driver receiver 543 rotates, and acompression mode, in which the movable body 541 b moves toward orapproximates the stationary body 541 b as the driver receiver 543rotates.

In use, once one or more pedicle screw assemblies 100 are installed intoadjacent vertebrae, and a spinal rod “R” is reduced into the pediclescrew housings 120 thereof, one or more drivers 520 may be introducedinto the pedicle screw assemblies 100 to tighten a set screw “S” againstthe spinal rod “R” to facilitate seating of the spinal rod “R,” forexample. The fulcrum 530 can be mounted to the bosses 522 of each driver520 to support the drivers 520 relative to one another. The distractionand compression instrument 540 can be coupled to adjacent drivers 520with the wings 542 a, 542 b of the stationary and movable bodies 541 a,541 b, respectively, positioned in contact with the adjacent drivers520. The driver receiver 543 can then be rotated to move the movablebody 541 b relative to the stationary body 541 a of the distraction andcompression instrument 540. Depending on whether the switch 544 is inthe compression or distraction mode, the wings 542 a, 542 b of thestationary and movable bodies 541 a, 541 b, respectively, will eithercompress or distract the drivers 520 relative to one another as desiredto cause a corresponding separation and/or distraction of one or morevertebrae of the spinal column to which the surgical system 500 isattached. When the spinal column, or portion thereof are in a desiredposition, one or more set screw “S” can be tightened as necessary tosecure or fix the position of one or more of the spinal rods “R” and/orone or more of the pedicle screw assemblies 100.

One or more of the components of the surgical system 500 can then beremoved from the pedicle screw assemblies 100 and the frangible members132 b, 134 b, 156 a, and 156 b (FIG. 2) thereof can be broken to remove,for example, the extension assemblies 140 of the pedicle screwassemblies 100 from the respective pedicle screw housings 120 (with theone or more spinal rods “R” secured thereto for maintaining the spine ina corrected position) as described herein or as detailed inInternational Application No. PCT/US16/46523 incorporated herein byreference.

With reference to FIG. 22, a surgical system in accordance with anotherembodiment of the present disclosure is shown and generally designatedas 600 may include, or be used with, any of the presently disclosed rodreducing assemblies.

With reference to FIGS. 23A, 23B, 24A, 24B, 25, and 26, a surgicalsystem in accordance with another embodiment of the present disclosureis shown and generally designated 700. The surgical system 700 may beused to manipulate the spine while inhibiting the frangible members 132b, 134 b and 156 a, 156 b of the tab and head assemblies 130, 150 of thepedicle screw assembly 100, respectively, from breaking as the set screw“S” is driven into the pedicle screw housing 120 of the pedicle screwassembly 100.

The surgical system 700 generally includes a pedicle screw assembly 100,a driver 710, a support sleeve 720, and an anti-torque tool 730. Thedriver 710 is used for rotating the set screw “S” into the pedicle screwhousing 120 (FIG. 1) of the pedicle screw assembly 100. The supportsleeve 720 is selectively mountable to the pedicle screw assembly 100and is configured to support the pedicle screw assembly 100 as the setscrew “S” is reduced into the pedicle screw assembly 100. Theanti-torque tool 730 is configured to selectively attach to the supportsleeve 720 to inhibit unwanted rotation of the pedicle screw assembly100 and the support sleeve 720, for example, as the driver 710 rotatesthe set screw “S” into the pedicle screw assembly 100.

The driver 710 of the surgical system 700 includes a handle 711 forgripping the driver 710, an elongated shaft 712 extending distally fromthe handle 711, and a driving bit 713 (FIG. 25) extending distally fromthe elongated shaft 712 and configured to engage and drive the set screw“S” into the pedicle screw housing 120 of the pedicle screw assembly100.

The support sleeve 720 of the surgical system 700 defines a longitudinalaxis “A4-A4.” Although shown with a cylindrically shaped body, thesupport sleeve 720 may have any suitable shape and/or configuration. Thesupport sleeve 720 includes an upper shaft portion 721 that extends to adistal surface 721 b and has a first gripping portion 721 a at proximalend, and which is configured for selective engagement with ananti-torque tool 730. The support sleeve 720 also defines a recessedportion 722 extending distally from the distal surface 721 b of theupper shaft portion 721 and recessed therefrom. The support sleeve 720further includes a tubular body 723 that extends distally from therecessed portion 722 and has a proximal end and a distal end. Theproximal end of the tubular body 723 of the support sleeve 720 has asecond gripping portion 723 a configured for engagement with theanti-torque tool 730.

The first gripping portion 721 a of the support sleeve 720 has asidewall 721 c defining one or more side surfaces 721 d positioned tofacilitate gripping and may be at the same or different angles relativeto each other. Similarly, the second gripping portion 723 a of thesupport sleeve 720 has a sidewall 723 b defining one or more sidesurfaces 723 c positioned to facilitate gripping and, may be at the sameor different angles relative to each other. In certain embodiments, oneor both of the sidewalls 721 c, 723 b of the respective first and secondgripping portions 721 a, 723 a of the support sleeve 720 may betextured, e.g., to facilitate gripping with anti-torque tool 730. Insome embodiments, the sidewalls 721 c, 723 b of the respective first andsecond gripping portions 721 a, 723 a of the support sleeve 720 maydefine and suitable circular and/or non-circular profile configured forengagement with a torqueing instrument, e.g., the anti-torque tool 730,for example, such profile may include one or more configurationsincluding hexagonal, star, square, circular, triangular, etc., and/orany combinations thereof.

In use, each of the first and second gripping portions 721 a, 723 a ofthe support sleeve 720 may be configured to receive one or moreanti-torque tools 730, separately, and/or simultaneously, as desired.With the first gripping portion 721 a positioned farther from thepatient than the second gripping portion 723 a, the first grippingportion 721 a may provide additional leverage for manipulating thevertebrae (given the larger moment arm relative to the patient'svertebrae) as compared to the second gripping portion 723 a.

The distal end of the tubular body 723 of the support sleeve 720 definesa first rod-engaging recess 724 a (FIG. 23A) on a first side of thetubular body 723 and a second rod-engaging recess 724 b (FIG. 24B) on asecond side of the tubular body 723. The first and second rod-engagingrecesses 724 a, 724 b are configured to engage the spinal rod “R” andmay have an inverted U-shaped or arched configuration. The supportsleeve 720 includes an inner surface 720 a that defines a hollow passage725 configured to selectively receive the pedicle screw assembly 100 andthe driver 710 therein. The support sleeve 720 defines elongatedchannels 726 a, 726 b therealong. The elongated channels 726 a, 726 bmay be configured to provide easy access to the inner surface 720 a ofsupport sleeve 720, e.g., for cleaning the inner surface 720 a of thesupport sleeve 720. The elongated channels 726 a, 726 b may act as,e.g., as a window to provide a visual of the location of pedicle screwassembly 100 relative to the support sleeve 720. The support sleeve 720may include indicia 727 (e.g., a laser marked line or the like) disposedon an outer surface of the tubular body 723 of the support sleeve 720.The indicia 727 can be used to determine the orientation of the pediclescrew assembly 100 relative to the support sleeve 720. For example, whenthe support sleeve 720 is fully seated onto the pedicle screw assembly100, the top or proximal end of the head assembly 150 of the pediclescrew assembly 100 may align with the indicia 727 of the support sleeve720.

With reference to FIG. 26, the anti-torque tool 730 of the surgicalsystem 700 includes an elongated shaft portion 731, a receiving member732 configured to engage one of the first or second gripping portions721 a, 723 a (FIG. 24A) of the support sleeve 720, a recess-receivingmember 733 configured to engage the recessed portion 722 of the supportsleeve 720, a knob 734 disposed along the elongated shaft portion 731and configured to impart movement to the recess-receiving member 733,and a pin 735 that couples the recess-receiving member 733 to the knob734.

The receiving member 732 of the anti-torque tool 730 has a firstgrasping portion 732 b that defines an opening 732 a. The first graspingportion 732 b may include one or more grasping surfaces 732 c with oneor more teeth configured to engage or grip the first or second grippingportions 721 a, 723 a of the support sleeve 720 to inhibit the supportsleeve 720 from rotating and/or to facilitate manipulation of thesupport sleeve 720 relative to the patient's vertebrae. The one or moregrasping surfaces 732 c of the first grasping portion 732 b may bepositioned at the same and/or different angles relative to one other.Similar to the first grasping portion 732 b, the recess-receiving member733 of the anti-torque tool 730 includes a second grasping portion 733 chaving one or more grasping surfaces 733 d that define an opening 733 bto enable the anti-torque tool 730 to grasp the recessed portion 722 ofthe support sleeve 720.

To operate the anti-torque tool 730, a force is applied to the knob 734of the anti-torque tool 730 in an axial (e.g., proximally) direction“X1” so that the knob 734 slides axially along elongated shaft portion731. By virtue of the recess-receiving member 733 being coupled to theknob 734 via the pin 735 of the anti-torque tool 730, the force appliedin the axial direction “X1” causes a corresponding movement of therecess-receiving member 733 in the axial direction “X1” such that therecess-receiving member 733 is retracted, e.g., proximally, andmisaligned with the receiving member 732. With the knob 734 coupled to areturn spring (not shown) disposed within the elongated shaft portion731 of the anti-torque tool 730, when the knob 734 is released, thereturn spring causes the knob 734 and the recess-receiving member 733 toreturn (e.g., distally) to an initial position in which therecess-receiving member 733 is aligned or substantially aligned with thereceiving member 732, as seen in FIG. 26.

In use, the pedicle screw assembly 100 of the surgical system 700 can beinstalled into a vertebra, and the spinal rod “R” can be reduced intothe pedicle screw housing 120 of the pedicle screw assembly 100. Thesupport sleeve 720 of the surgical system 700 can be placed over, andadvanced onto, the pedicle screw assembly 100 until the first and secondrod-engaging recesses 724 a, 724 b of the support sleeve 720 engage thespinal rod “R.” As desired, the anti-torque tool 730 can be placed ontothe support sleeve 720.

To attach the anti-torque tool 730 to the support sleeve 720, forexample, to one of the first or second gripping portions 721 a, 723 a ofthe support sleeve 720, the knob 734 of the anti-torque tool 730 can bepulled back in the axial direction “X1” by applying a force in the axialdirection “X1,” which causes the recess-receiving member 733 to bepulled back or retracted in the axial direction “X1.” The receivingmember 732 of the anti-torque tool 730 can be advanced toward thesupport sleeve 720 until the grasping portion 732 b of the receivingmember 732 of the anti-torque tool 730 surrounds a respective one of thefirst or second gripping portions 721 a, 723 a of the support sleeve720. The anti-torque tool 730 can be moved down or distally onto therespective one of the first or second gripping portions 721 a, 723 a ofthe support sleeve 720 until the grasping portion 732 b of the receivingmember 732 of the anti-torque tool 730 engages with one of the first orsecond gripping portions 721 a, 723 a of the support sleeve 720.

With respect to the second gripping portion 723 a of the support sleeve720, in order to lock the anti-torque tool 730 onto the support sleeve720, force applied to the knob 734 can be released, which causesrecess-receiving member 733 to return (e.g., via the return spring, notshown) or snap back to the rest or initial position and engage thesupport sleeve 720. For example, with respect to the second grippingportion 723 a of the support sleeve 720, as the recess-receiving member733 returns, the recess-receiving member 733 becomes wedged between thereceiving member 732 and the distal surface 721 b of the upper shaftportion 721 of the support sleeve 720. Once the receiving member 733 isbiased back to its initial position and secured to the support sleeve720, the anti-torque tool 730 is locked onto the support sleeve 720 andis inhibited from premature removal from the support sleeve 720. Thedriver 710 of the surgical system 700 may be introduced into the pediclescrew assembly 100 and the support sleeve 720 to tighten the set screw“S with the driving bit 713 of the driver 710. As the set screw “S” istightened against the spinal rod “R,” the spinal rod “R” is driven orseated into the pedicle screw housing 120 of the pedicle screw assembly100. While tightening the set screw “S,” a clinician may firmly graspthe elongated shaft portion 731 of the anti-torque tool 730 to inhibitthe support sleeve 720 and/or the pedicle screw assembly 100 fromrotating (e.g., rotationally fix) to facilitate driving and/ortightening of the set screw “S” so that the set screw “S” can secure thespinal rod “R” to the pedicle screw assembly 100. Once the set screw “S”is secured to the spinal rod “R,” the driver 710 may be withdrawnproximally from the support sleeve 720.

To remove the anti-torque tool 730 from the support sleeve 720 withrespect to either the first or second gripping portions 721 a, 723 a ofthe support sleeve 720, the anti-torque tool 730 can be moved up orproximally off, the first or second gripping portions 721 a, 723 a ofthe support sleeve 720 until the grasping portion 732 b of the receivingmember 732 of the anti-torque tool 730 is disengaged from the respectivefirst or second gripping portions 721 a, 723 a of the support sleeve720. The support sleeve 720 may then be moved proximally away from thepedicle screw assembly 100 to remove the support sleeve 720 from thepedicle screw assembly 100 and, e.g., out of a body cavity.

Alternatively, and or additionally, to remove the anti-torque tool 730from the second gripping portion 723 a of the support sleeve 720, forcein the axial direction “X1” can be applied to the knob 734 of theanti-torque tool 730 to retract the recess-receiving member 733 anddisengage the recess-receiving member 733 from the recessed portion 722.With the recess-receiving member 733 of the anti-torque tool 730disengaged from the recessed portion 722 of the support sleeve 720, therecess-receiving member 733 is no longer wedged between the distalsurface 721 b of the upper shaft portion 721 of the support sleeve 720and the receiving member 732 of the anti-torque tool 730 so that theanti-torque tool 730 can be separated from the support sleeve 720.

Persons skilled in the art will understand that the structures andmethods specifically described herein and shown in the accompanyingfigures are non-limiting exemplary embodiments, and that thedescription, disclosure, and figures should be construed merely asexemplary of particular embodiments. It is to be understood, therefore,that the present disclosure is not limited to the precise embodimentsdescribed, and that various other changes and modifications may beeffected by one skilled in the art without departing from the scope orspirit of the disclosure. Additionally, the elements and features shownor described in connection with certain embodiments may be combined withthe elements and features of certain other embodiments without departingfrom the scope of the present disclosure, and that such modificationsand variations are also included within the scope of the presentdisclosure. Accordingly, the subject matter of the present disclosure isnot limited by what has been particularly shown and described.

1. A system for spinal surgery, comprising: a pedicle screw assemblyincluding a screw securable to a spinal bone and a pedicle screw housingcoupled to the screw, the pedicle screw housing defining a rod-receivingrecess, the pedicle screw assembly including an extension assemblycoupled to the pedicle screw housing by a frangible member; a derotationsleeve mountable to the pedicle screw assembly, the derotation sleevemovable with the pedicle screw assembly to manipulate the spinal bone,the derotation sleeve configured to inhibit the frangible member frombreaking while manipulating the spinal bone; and a rod reducer mountableto the derotation sleeve and configured to reduce a spinal rod into therod-receiving recess of the pedicle screw.
 2. The system of claim 1,wherein the derotation sleeve includes a locking mechanism positionablebetween a locked position and an unlocked position, the derotationsleeve secured to the pedicle screw assembly while in the lockedposition, the derotation sleeve separable from the pedicle screwassembly while in the unlocked position.
 3. The system of claim 2,wherein the derotation sleeve includes an upper shaft portion and alower shaft portion coupled to the upper shaft portion, the upper shaftportion being movable relative to the lower shaft portion to positionthe locking mechanism between the locked and unlocked positions.
 4. Thesystem of claim 3, wherein the upper shaft portion of the derotationsleeve includes a sleeve assembly including an inner sleeve and an outersleeve, the inner sleeve selectively attachable to the extensionassembly of the pedicle screw assembly to secure the derotation sleeveto the pedicle screw assembly.
 5. The system of claim 4, wherein theinner sleeve includes a finger and the extension assembly defines agroove configured to selectively receive the finger.
 6. The system ofclaim 4, wherein the derotation sleeve includes a knob rotatablerelative to the inner sleeve to move the outer sleeve axially relativeto the inner sleeve until the outer sleeve engages the lower shaftportion to restrain movement of the upper shaft portion relative to thelower shaft portion when the locking mechanism is positioned in thelocked position.
 7. The system of claim 1, wherein the rod reducerincludes a cap that is threadably engagable with a proximal end of thederotation sleeve to couple the rod reducer to the derotation sleeve. 8.The system of claim 7, wherein the cap of the rod reducer is coupled toa sleeve assembly of the rod reducer, the sleeve assembly of the rodreducer includes an outer sleeve and an inner sleeve, the outer sleeveof the rod reducer is rotatable relative to the cap and the inner sleeveof the rod reducer to axially advance the inner sleeve of the rodreducer along the pedicle screw assembly and reduce the spinal rod intothe rod-receiving recess of the pedicle screw housing of the pediclescrew assembly.
 9. A system for spinal surgery, comprising: a pediclescrew assembly including a screw securable to a spinal bone and apedicle screw housing coupled to the screw, the pedicle screw housingdefining a rod-receiving recess, the pedicle screw assembly including anextension assembly coupled to the pedicle screw housing and extendingproximally therefrom; a derotation sleeve mountable to the pedicle screwassembly, the derotation sleeve having a locking member for securelyengaging a locking feature of the extension assembly to preventseparation of the derotation sleeve from the pedicle screw assembly;wherein a proximal portion of the derotation sleeve is rotatable about alongitudinal axis of the derotation sleeve with respect to a distalportion of the derotation sleeve to move the locking member out ofengagement with the locking feature.
 10. The system of claim 9, whereinthe locking feature is a groove elongated in a direction transverse to alongitudinal dimension of the extension assembly.
 11. The system ofclaim 10, wherein the locking member is a finger deflectable to snapinto the groove.
 12. The system of claim 11, wherein rotation of theproximal portion of the derotation sleeve about the longitudinal axiscauses the finger to cam out of the groove.
 13. The system of claim 9,wherein the proximal portion of the derotation sleeve is lockable toprevent rotation of the proximal portion with respect to the distalportion.
 14. The system of claim 13, wherein the proximal portion of thederotation sleeve is lockable by rotating a knob of the derotationsleeve about the longitudinal axis.
 15. The system of claim 13, whereinthe proximal portion of the derotation sleeve is lockable by advancingthe proximal portion distally towards the distal portion.
 16. The systemof claim 14, wherein advancing the proximal portion of the derotationsleeve distally towards the distal portion includes causing teeth toengage corresponding recesses at an interface between the proximalportion and the distal portion of the derotation sleeve.
 17. The systemof claim 9, wherein the extension assembly of the pedicle screw assemblyincludes a pair of longitudinal extensions, each of the longitudinalextensions extending proximally from a respective distal end coupled tothe pedicle screw housing, and wherein the derotation sleeve includes afirst leg and a second leg spaced apart from one another and elongatedalong a longitudinal direction parallel to the longitudinal axis, eachof the first and second legs being configured to be positioned alongsidea respective one of the pair of longitudinal extensions when thederotation sleeve is mounted to the pedicle screw assembly.
 18. Thesystem of claim 17, wherein each of the longitudinal extensions of thepedicle screw assembly is coupled to the pedicle screw housing by arespective frangible member, and wherein each of the first and secondlegs is configured to extend adjacent to a respective one of thefrangible members when the derotation sleeve is mounted to the pediclescrew assembly.
 19. The system of claim 9, further including a rodreducer securable over the derotation sleeve and configured to reduce aspinal rod into the rod-receiving recess of the pedicle screw.
 20. Thesystem of claim 19, wherein the rod reducer has a proximal portionsecurable to a proximal end of the derotation sleeve, the rod reducerincluding a sleeve portion extending distally from the proximal portion,the sleeve portion being advanceable distally along the longitudinalaxis to push the spinal rod distally when the rod reducer is secured tothe derotation sleeve.